Arc welding

Bernandos (1887) and Kjellberg (1914) were the first to use the melting power of an electric arc to weld metals. Energy is supplied by a bank of accumulators, and welding is performed using an electrode that melts progressively, then solidifies into a deposit that combines intimately with the metal of the parts to form a continuous bond. The process developed mainly thanks to the development of a cellulose-coated electrode which, because it vaporizes to form a protective screen, fulfils the imperative condition, for healthy welds, of removing the molten metals from the action of the air. The fundamental principles of all fusible metal arc welding processes have now been established, as have to some extent the principles of refractory electrode processes.

In this way, we realize that the phenomena that take place in an arc welding bath are foundry phenomena, as opposed to forge phenomena.

The advent of the various arc-based processes then unfolds step by step in a logical fashion:

• the coating becomes mineral and more controllable;

• the metal core of the electrode in limited sections becomes a continuous wire with a coating supplied directly in powder form;

• the coating is replaced by an easier-to-use gas;

• the electrode may also be refractory.

These modifications led to the four fundamental processes that today form the basic arc welding toolbox.

This article describes the electrical and thermal laws of the arc common to these four processes, and then develops the most important principles and characteristics for each of them and some of their variants. An understanding of these basic principles will make clear the particularities that govern their specific applications and implementation. The presentation follows the historical order, which is logical from a theoretical and practical point of view, of the appearance of the processes, so that other classifications can be understood without difficulty. The various ways of applying the processes examined, based on common or related principles, are discussed in a separate paragraph.

Readers may also wish to refer to the article for different welding processes.